The lithosphere is composed of both the crust and the portion of the upper mantle that behaves as a brittle, rigid solid. The definition of the lithosphere is based on how Earth materials behave, so i...The lithosphere is composed of both the crust and the portion of the upper mantle that behaves as a brittle, rigid solid. The definition of the lithosphere is based on how Earth materials behave, so it includes the crust and the uppermost mantle, which are both brittle. What are the mechanical properties of the material below the lithosphere and what is the layer called? What is the composition and mechanical property of the mesosphere relative to the asthenosphere?
